userspace/rootfs_override: save date of last update

Note: Be aware that date of last update may be not accurate.
One reason is that it uses date stored before last restart, so time needed to restart is not taken into account.
Additionally date stored before restart may be not accurate for many reasons like:
--hard restart (last know date was not saved)
--date was never received from ntp nor set manually

Signed-off-by: Adam Wujek <adam.wujek@cern.ch>

userspace/rootfs_override/etc/init.d/wrs-boot-procedure

@@ -123,6 +123,9 @@ mount -t ubifs ubi0:boot /boot
 # Some steps later set reboot=true; prepare a sane default.
 reboot=false
 
+#whether to change date of last update
+change_update_date=false
+
 # First: update usr: we may have the whole thing, or just wrs-usr.tar.gz
 if [ -f /update/$WRS_FW -o -f /update/$WRS_USR ]; then
     # FIXME: save configuration somewhere, and recover it later
@@ -171,7 +174,7 @@ if [ -f /update/$WRS_FW -o -f /update/$WRS_USR ]; then
     fi
     # And, to be sure, remove a file that may exist from a 4.0 install
     rm -f /update/$OLD_FW_OLDNAME
-
+    change_update_date=true
 fi
 
 # Allow replacing the kernel or initramfs alone (new in v4.1 of wr-switch-sw)
@@ -190,8 +193,12 @@ if [ -f /update/$WRS_BB ]; then
     mv /update/current-$WRS_BB /update/previous-$WRS_BB
     mv /update/$WRS_BB /update/current-$WRS_BB
     reboot=true
+    change_update_date=true
 fi
 
+if $change_update_date; then
+    cp /update/saved_date /update/last_update > /dev/null 2>&1
+fi
 # If we changed bloader or kernel or initramfs, we reboot. Otherwise proceed.
 if $reboot; then
     umount /update